Several families of RNA-binding proteins are involved in a variety of fundamental cellular processes including RNA splicing, polyadenylation, RNA transport, and translation. Members of the RNA recognition motif (RRM)/ribonucleoprotein (RNP) family contain one to four approximately 100 amino acid long RRM domains in association with various auxiliary domains. TIAR is a RRM protein that is comprised of three N-terminal RRM domains and a C-terminal auxiliary domain (Beck et al., Nucleic Acid Research 24: 3829-3835, 1996; Dember et al., J. Biol. Chem 271: 2783-2788, 1996; Taupin et al., Proc. Natl. Acad. Sci. USA 92: 1629-1633, 1995; Tian et al., Cell 67: 629-639, 1991). Murine TIAR is predominantly expressed in brain, testis, and spleen. At least two isoforms of the protein are generated by alternative splicing (FIG. 1).